The present invention relates generally to crop harvesting headers attachable to a combine to initiate the crop harvesting process and, more particularly, to a pneumatic control mechanism for automatically adjusting the height of the header so that the header will follow changing longitudinal ground contours.
Header height control systems for combines have utilized electrically controlled hydraulic valves. Such systems can result in a larger load loss in the hydraulic system because of the need to intersperse a solenoid valve into the system, causing a larger heat generation into the hydraulic circuit. Furthermore, electrical microswitches are generally fragile and deteriorate easily when utilized in the farm machinery environment, particularly when exposed to grain residues, dust, weather conditions, etc. Accordingly, it would be desirable to provide an improved header height control mechanism to simplify the operation of the mechanism, reduce costs, simplify maintenance and improve durability.